Molecular Design of a Room-Temperature Maser

A computational molecular design strategy, complemented by UV/vis absorption and time-resolved electron paramagnetic resonance (EPR) spectra measurements, is employed to guide the search for active molecules for a room temperature maser that can achieve continuous-wave operation. Focusing on linear polyacenes and diaza-substituted forms, our goal is to model how important maser properties are influenced by acene length and location of nitrogen substitution. We find that tetracene, its diaza-substituted forms (5,11-, 1,7-, and 2,8-diazatetracene), and anthracene possess singlet to triplet intersystem crossing rates highly favorable toward masing. The diaza-substituted forms of pentacene (6,13-, 5,12-, 1,8-, and 2,9-diazapentacene) also stand out as ideal candidates due to their similarity to the working pentacene prototype. A steady-state population analysis suggests the working conditions under which continuous-wave masing can be achieved for these molecules. Operational frequencies are estimated from calculated zero field splitting parameters.